A conventional frequency shift-keying reader circuit comprises a band-pass filter, an injection-locked oscillator and a multiplier. The low-pass filter receives an input signal and performs a filtering procedure to the input signal. The injection locked oscillator receives the filtered input signal. Besides, the injection-locked oscillator is locked by the filtered input signal and outputs an oscillation signal. The input signal and the oscillation signal are received by the multiplier so as to perform a mixing procedure. Thereafter, an output signal is outputted from a low-pass filter after a filtering procedure of the low-pass filter. The operational frequency of modern wireless radio frequency achieves Giga Hertz level, the higher the operational frequency, the larger the power consumption for the frequency shift-keying reader circuit. Therefore, the conventional frequency shift-keying reader circuit acquires stable demodulating quality under the condition of high DC power consumption. The conventional frequency shift-keying reader circuit does not meet the Spec demand of short distance wireless communication characterized in low power consumption. Besides, owing to low isolation from the local oscillation port of the conventional frequency shift-keying reader circuit to the radio frequency signal, the output signal outputted from the multiplier further includes a self-mixing component of local oscillation signal. The self-mixing component is a DC displacement therefore increasing the bit error rate of the demodulating signal.